The terms oil/tar sands, often referred to as ‘extra heavy oil,’ are types of bitumen deposits. The deposits are naturally occurring mixtures of sand or clay, water and an extremely dense and viscous form of petroleum called bitumen. They are found in large amounts in many countries throughout the world, but are found in extremely large quantities in Canada and Venezuela.
Due to the fact that extra-heavy oil and bitumen flow very slowly, if at all, toward producing wells under normal reservoir conditions, the sands are often extracted by strip mining or the oil made to flow into wells by in situ techniques which reduce the viscosity by injecting steam, solvents, and/or hot air into the sands. These processes can use more water and require larger amounts of energy than conventional oil extraction, although many conventional oil fields also require large amounts of water and energy to achieve good rates of production.
Like all mining and non-renewable resource development projects, oil sands operations have an effect on the environment. Oil sands projects may affect the land when the bitumen is initially mined and with large deposits of toxic chemicals, the water during the separation process and through the drainage of rivers, and the air due to the release of carbon dioxide and other emissions, as well as deforestation. Clearly any improvements in the techniques use to extract hydrocarbonaceous products from shale and sands would be appreciated, particularly if efficiency is improved and/or environmental impact is reduced.
Certain improvements with respect to the recovery of products from oil shales are disclosed in U.S. Pat. No. 7,041,051. Unlike other prior art processes, the in situ body of oil sands to be treated is not surface mined. Rather, the process includes drilling a hole in the body of oil sands, and locating a processing gas inlet conduit within the hole such that the bottom end of the processing inlet gas conduit is near the bottom of the hole. An effluent gas conduit is anchored around the opening of the hole at the ground surface of the body of oil sand. A processing gas is introduced into an above-ground combustor. In the combustor, the processing gas, which contains enough oxygen to support combustion, is heated by burning a combustible material introduced into the combustor in the presence of the processing gas. The resultant heated processing gas is of a temperature sufficient to convert kerogen in the oil shale to gaseous hydrocarbonaceous products.
The heat from the heated processing gas, as well as radiant heat from the processing gas inlet conduit, create a nonburning thermal energy front in the oil sands surrounding the hole. The bitumen is thus pyrolyzed and converted into hydrocarbonaceous products. The products produced during pyrolysis of the bitumen are in gaseous form and are withdrawn with the processing gas as an effluent gas through the hole and into the effluent gas conduit. The effluent gas is transferred through the effluent gas conduit into a condenser where the effluent gas is allowed to expand and cool so as to condense a portion of the hydrocarbonaceous products into liquid fractions. In the condenser, a remaining gaseous fraction of hydrocarbonaceous products is separated from the liquid fraction of hydrocarbonaceous products. The gaseous fraction is preferably filtered and or scrubbed so as to separate the upgraded gas products from any waste gases including the inorganic gas carbon dioxide.
A portion of the upgraded hydrocarbon gas may be recycled to the combustor to provide combustible material for fueling combustion within the combustor, and while a portion of the waste inorganic gas may be recycled to the compressor for augmenting the supply of carbon dioxide in the processing gas, further improvements are possible, both in the generation of the heated, processing gas as well as the recovery of products and byproducts produced in the condenser.